Electric water heater



March 19, 1935. T, HARVEY 1,994,765

ELECTRIC WATER HEATER.

Filed Feb; 12, 1934 resistance element, and my object is to devise a Patented Mar. 19, 1935 PATENT OFFICE ELECTRIC WATER HEATER Thomas Harvey, Toronto, Ontario, Canada Application February 12, 1934, Serial No. 710,768 In Canada March 25, 1933 9 Claims.

This invention relates to water heaters of the type adapted for connection to a tank and in which the water is heated by causing it to flow over heat transfer surfaces heated by an electric simple, 11 ged, and economical heater particularly adapted for use where electrical energy is available at a fiat rate.

I attain my object by means of constructions which may be briefly described as follows: The heater is long, relative to its energy consumption, whereby the heating element may be readily made long enough to operate at a relatively low temperature and adequate area of heat exchange surface obtained using water tubes of relatively small diameter. The heater is formed of three concentric tubes forming two longitudinal waterways, the inner of less cross sectional area than the outer, the inner tubes enclosing between them a suitably insulated resistance element. The inflowing water thus flows upwardly in two columns, the water flowing in the inner waterway being at a higher temperature than that in the outer waterway since the cross sectional area of this water column is smaller in proportion to the heating surface of the inner tube than the ratio of the cross sectional area of the outer water column to the heating surface of the intermediate tube. An injectional effect is thus obtained at the outlet of the inner tube which markedly increases the rate of movement of the outer water column. This effect is markedly increased by contracting the said outlet preferably to a diameter about one-half that of the body of the tube. In any case the outlet of the inner tube is always materially less in diameter than the outlet of the outer water column. The inner and intermediate tubes are connected with a plug screwed into the lower end of the outer tube. Two separate resistance coils are provided, one of which may be connected directly to a source of'electrical energy and the other through a meter.

The invention is hereinafter more specifically described and is illustrated in the accompanying drawing in'which Fig. 1 is a longitudinal section of my improved heater;

Fig. 2 a cross section on the line 22 in Fig. l Fig. 3 a cross section on the line 33 in Fig. 1; and

Fig. 4 a diagram of the resistance wiring. In the drawing like numerals of reference indicate corresponding parts in the different figures. In the drawing 1 is an inlet connection of standard type and 2 an outlet connection having its outlet opposite to and smaller than its inlet end. Into these connections are threaded the ends of a tube 3. The inlet 19 of the inlet connection 1 is laterally directed for connection with the lower part of a reservoir or tank, while the outlet connection 2 is connected with the elbow 6 for connection with the upper part of a reservoir tank. The lower opening of the inlet connection 1 has a plug 7 screwed therein. This plug has an opening formed therethrough into which is sweated the lower end of a tube 4, which tube is thus spaced from the tube 3 to form an annular waterway. Centrally positioned within the tube 4 is the inner tube 5 which extends up to the upper end of the tube 3 close to the connection. The lower end of the tube is formed with the elbow 20, which opens through and is secured to the wall of the tube 4 opposite the inlet opening 19. The cross-sectional area of the tube 5 is considerably less than that of the annular water space formed by the tubes 3 and 4. Thus the heating surface of the inner tube is much greater relative to the volume of water contained therein than that of the heating surface of the tube 4 relative to the volume of water contained in the annular waterway. From this it follows that higher temperatures are attained in the inner waterway than in the annular waterway.

The space between the tubes 4 and 5 is closed at the lower end owing to the fact that the tube 4 is inserted into the plug '7. At the upper ends of these tubes the space between the tubes is closed by spinning in the end of the tube 4 as indicated at 8. The upper end of the tube 5 is also preferably spun in as indicated at 9 to reduce the area of the water outlet from the tube 5. In the space between the tubes 4 and 5 is contained a resistance wiring. This wiring 10 is formed in two circuits in a manner known in the art, the separate circuits being connected with the terminals 13 which are necessarily four in number (see Figs. 1, 3 and 4).

The resistance wiring is embedded in a mixture of asbestos and plaster of Paris set with water. I have found that such a mixture provides the necessary electrical insulation and is at thesame time sufficiently heat conductive. In preparing the heating elements the tube 5 is first coated with a layer of the plaster of Paris and asbestos. The resistance wiring is then wound thereon and embedded in the mixture in a suitable mould. The inner tube, with the wiring in place thereon embedded in the mixture, is then positioned in the tube 4 and the upper ends of the tubes spun in as hereinbefore described and brazed as may be necessary. The lower end of the tube 4 is then sweated in place in the plug '7. The projecting ends of the resistance wiring are then connected to the terminal bolts 13, which extend through an insulating block 12, which may then be positioned in the opening in the plug 7. To the outer ends of the terminals are connected the leads .14, one pair of which will usually lead directly to a source of electrical energy while the other pair will be connected with a meter.

A cylindrical guard 15 is secured to the inlet connection 1 by means of the screws .18. To an opening in this guard is secured a conduit 21 through which the leads 14 pass. A cover l6 is hinged at 18 to the fixed part of the guard 15 and is normally held closed by one of the screws 18. The guard is thus readily opened up when desired to obtain access to the terminals 13.

The mode of operation of the device is substantially as follows: Cold water from a reser-' voir or tank flows into the inlet connection 1 in which the how is divided, part passing up through the outer annular waterway and part through the inner tube 5. From the arrangement and propor-tioning of the waterways it follows that a jet of hot water at a relatively high velocity is injected into the outlet connection 2, materially aiding the circulation of water through the annular waterway and raising its temperature. It is important, of course, that the outlet from the connection 2 should be materially great er in diameter than the outlet of the inner tube 5, while the lower end of the connection is of substantially the same diameter as the tube 3.

I have found that, for a flat rate current consumption of 500 watts and a meter consumption soc watts more, the waterways of the heater should be in the neighborhood of 40 inches in 1ength,-though, of course, I do not restrict myself to these proportions.

From the above description it will be seen that 1 have devised a water heater which will satisfactorily attain the objects of my invention as set out in the preamble to this specification.

What I claim as my invention is:

1. An electric water heater comprising three concentric tubes forming two upright waterways, one within the inner tube and 'one between the outer and intermediate tubes; a Water inlet connection with which'both waterways connect;

within the inner tube and one between the outer and intermediate tubes; a water inlet connection with which both waterways connect; a water outlet connection with which both waterways com' municate; a plug to which the inner and intermediate tubes are connected and which is detachably secured to close an opening in the lower end or" the inlet connection; and suitably insulated resistance wiring contained between the inner and intermediate tubes.

3. An el ctric water heater comprising three concentric tubes forming two waterways, one

within the inner tube and one between the outer and intermediate tubes; a water inlet connection with which both waterways connect; a water outlet connection with which both waterways communicate; a plug to which the inner and intermediate tubes are connected and which is detachably secured to close an opening in the lower end of the inlet connection; suitably insulated resistance wiring contained between the inner and intermediate tubes; a block of insulating material inserted in an opening in the plug aforesaid; and terminals for the resistance wiring carried by the said block.

4. An electric water heater comprising three concentric tubes forming two waterways, one within the inner tube and one between the outer and intermediate tubes; a water inlet connection with which both waterways connect; a water outlet connection with which both waterways communicate; a filling of a water set mixture of plaster of Paris and asbestos between the inner and intermediate tubes; and resistance wiring embedded in the said mixture.

5. An electric water heater according to claim 1 in which the communication between the inner tube and the inlet is formed by a bend at the lower end of the inner tube connected with an opening in the side of the intermediate tube.

6. An electric water heater comprising three concentric tubes forming two waterways, one within the inner tube and one between the outer and intermediate tubes; a water inlet connection with which both waterways connect; a water outlet connection with which both waterways communicate; a plug to which the inner and intermediate tubes are connected and which is detachably secured to close an. opening in the lower end of the inlet connection; suitably insulated resistance wiring contained between the inner and intermediate tubes; a block of insulating material inserted in an opening in the plug aforesaid; terminals for the resistance wiring carried by the said block; and a cylindrical guard for the terminals secured to the inlet connection and provided with an opening and a closure for said opening.

7. An electric water heater comprising three concentric tubes forming two waterways; an outlet connection with which both waterways communicate; a water inlet connection of T formhaving the stem of the T extending laterally, the outer tube aforesaid being connected with one end of the head of the T; a plug detachably secured in the other end of the head of the T, the intermediate tube being connected to the plug while the inner tube opens into the connection through the side of the intermediate tube; and suitably insulated resistance wiring, contained between the inner and intermediate tubes.

8. An electric water heater comprising three concentric tubes forming two waterways; an outlet connection with which both waterways communicate; a water inlet connection of T form having the stem of the T extending laterally, the outer tube aforesaid being connected with one end of the head of the T; a plug detachably secured in the other end of the head of the T, the intermediate tube being connected to the plug while the inner. tube opens into the connection through the side of the intermediate tube; suitably insulated resistance wiring contained between the inner and intermediate tubes; a block of insulating material inserted in an opening in said plug; and terminals for the resistance wiring carried by the said block.

lower end of the intermediate tube; suitably insulated resistance wiring contained between the inner and intermediate tubes; connections for said wiring extending through the plug aforesaid; and a. water outlet connection with which both waterways connect.

THOMAS HARVEY. 

